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Pearl dual output mics
Old 7th July 2020
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Pearl dual output mics

Hi all,

I've appreciated the "rectangular capsule users, unite!" and other threads here on the forums, but hope to get some feedback specifically on the two Pearl dual-output models, ELM-A and TL44.
I demo'd a pair of ELM-B (the fixed pattern, figure eight model) several months ago and was very impressed by them. I am well aware already of the basic differences between the two microphones in terms of the ELM's higher directivity, somewhat lower noise than TL44, etc.

Although it will likely be some time, with the current live recording landscape, before I make another microphone purchase, I have been increasingly interested in the various dual-output microphones available, primarily for their obvious flexibility.

I am already a big fan of the Pearl sound, and do not need any convincing that they can produce lovely recordings -- my questions are more pragmatic. For anyone who has experience with either or both of these Pearl models, my questions are:

1. How do you find them, in a classical/acoustic main system role, in comparison to more familiar dual-output staples like the Sennheiser MKH800 Twin? Or even newcomers like the Austrian Audio OC818?

2. Having not yet had the opportunity to demo the ELM-series mics in a large ensemble recording context, it is difficult for me to know how well they might function. For something as large (or larger) than, say, a chamber orchestra, I am wondering if the vertical plane directivity (assuming an upright orientation) would make their pickup too narrow to adequately capture an ensemble with a larger front-to-back footprint. In this regard, I wonder how much better the TL44 might fare? Again, I have thus far only experienced the longer-membrane ELM-B.

3. The vast majority of recordings I have heard with Pearl microphones involve a directional pickup, either via their cardioid models or the DS60 -- however, whenever possible I prefer to record using omnis. Any feedback about how the Pearls perform in omni mode? Challenges, surprising benefits, etc. would all be welcome information.

Many thanks, as always, for any input!

Hope those of us who are currently more or less sidelined can get back to recording music again as soon as it is feasible

Last edited by lukedamrosch; 8th July 2020 at 03:04 PM.. Reason: clarification
Old 22nd July 2020
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Just wanted to give this thread a bump, on the off-chance anyone missed it the first time around.

I realize the topic is pretty esoteric, and will certainly not continue to repeat this process!
Old 23rd July 2020
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Quote:
Originally Posted by lukedamrosch View Post
Just wanted to give this thread a bump, on the off-chance anyone missed it the first time around.

I realize the topic is pretty esoteric, and will certainly not continue to repeat this process!
I really wanted to comment on this the first time I saw it, but felt like I didn’t have much to offer that you didn’t already know. However, now that you’ve mentioned it again and you’re not getting any bites, here are some thoughts...

I love the sound and build quality of the ELM series; I reviewed the cardioid model years ago and was well-impressed. They’re quite unique in a good sounding way. I have yet to hear a recording made with the ELMs that did not sound, at the very least, acceptable. Most sound lovely.

In 2017 I was cashed up to buy my ‘desert island mic pair’. A pair of ELM-As was high on that list, but my ‘desert island recorder’ was a Nagra 7 with only two mic inputs. I sent an email to Pearl asking about some passive circuits I’d drawn up to go in small in-line barrels mounted between the mics and the Nagra so I could change polar responses on the job; each barrel would contain a simple summing network that would give me either bidirectional, cardioid or omni (one per barrel) assuming a) the ELM-A gave differential outputs (rather than impedance balanced with signal on one pin only), and B) the circuit didn’t affect the phantom powering significantly. I didn’t get a reply, and ended up going with a matched pair of MKH800s. No regrets, but I still lust after a pair of ELM-As. If Pearl brought out an updated version with switchable polar response you’d be seeing my Mum on Ebay.

Regarding the rectangular diaphragm with larger ensembles, I find it is handy to have the narrower directionality in the vertical plane. The link below is a chamber ensemble I recorded with a pair of Milab DC196s, which also have rectangular diaphragms but not as long as the ELMs. I intentionally relied on that increased directionality in the vertical plane to balance the woodwinds at the back of the stage against the strings at the front. It’s not a perfect recording, but I think it’s not bad for a recording where the rules were ‘no mics on stage’ and there are only two winches. I suspect if I was using ELM-As their increased directivity in the vertical plane would’ve helped me balance things out even better.

https://youtu.be/5g9Hvb_RB4c

Last edited by Simmosonic; 23rd July 2020 at 06:00 AM..
Old 23rd July 2020
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Hi Greg,

Many thanks for taking the time to share these thoughts. I really appreciate them, as well as some others I recall from your excellent and thoughtful review in Audio Technology of the ELM-C (which, incidentally, I did not happen upon until after demo'ing the ELM-B's I mentioned earlier).

From my limited experience, I'd say that your characterization of "quite unique in a good-sounding way" would be a pretty elegant summation of the Pearl ELM!

Thanks also for sharing that recording. It's very helpful to be able to see and hear a similar pair (and only the single pair) of mics in this kind of situation. This is a good example of the kind of situation where, on the one hand, I can imagine the ELM series being very useful -- however, on the other hand, my main concern remains:

Particularly with the longer 7:1 membrane, if one were in a typical, somewhat rushed, concert recording context, to what extent might the extra fine-tuning of vertical plane precision needed for good balancing potentially outweigh the benefits of the dual output flexibility (and other desirable Pearl qualities)?

I realize this is a very difficult question to speculate about, perhaps impossible without simply getting a range of experience with the ELM-A's specifically. But in any case, this is my main reservation about purchasing a pair.

On an unrelated note, did you happen to try the ELM-C in M-S configuration and, if so, with what mic(s) for the S channel? I'm curious how flexible (or not) the ELM mics may be in that scenario, bearing in mind the considerable geometric mismatch between a long rectangular membrane and (e.g.) a small circular one for the figure 8. Let the M-S purists descend and correct/ridicule this mere suggestion at their leisure

Thanks again for your comments!
Old 24th July 2020
  #5
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Quote:
Originally Posted by lukedamrosch View Post
Particularly with the longer 7:1 membrane, if one were in a typical, somewhat rushed, concert recording context, to what extent might the extra fine-tuning of vertical plane precision needed for good balancing potentially outweigh the benefits of the dual output flexibility (and other desirable Pearl qualities)?
Actually, this is a good point to raise. The Milab DC196s are much shorter diaphragms but even so it took me a while to get used to them, to hear what they were doing in the vertical plane, and then building that into my set-up approach so it was no longer random or trail and error. In the end, and this is more relevant to the ELMs, it’s just like setting up a ribbon mic. They have the same horizontal/vertical characteristics, which means the angle becomes really important.

I ended up taking an approach that followed my usual methodology, which is fast and efficient for me – bearing in mind that I’m usually setting up with the Nagra V over my shoulder and Etymotic canal phones, sitting on the ladder and/or with the winch control making adjustments and hearing their immediate effects rather than running back and forth between a control room and recording space. It’s a very fast and efficient way to work.

With that on-the-spot monitoring capability, I’ll start with the mics side by side (flush against each other) facing forward in whichever polar response I think is going to be most apt, monitoring in stereo via canal phones. In that configuration I’ll then work out height, distance and angle for the best balance and sense of ensemble. Once I’ve got that worked out, then I’ll space the mics apart to find the right width and imaging. Then I tweak from there. The longer diaphragms just add another element that gives me more front-to-back control. I like to think of a laser beam running perpendicular from the centre of the mic to the centre of the ensemble, check the front-to-back balance, and angle the mic so the laser is aiming more at what I need to get that balance right. That approach worked very well for me with the Milabs; in the linked recording and also in a handful of fast-set-up orchestral recordings that generated a flurry of excitement by the conductors, with just the Milabs in ORTF and using that front-to-back balancing idea. For me it was one more step in my usual approach, but it was also the difference between definitely needing spot mics or being able to get away without them – depending on the goal of the job. So I see that narrower vertical polar response as a bonus, not a problem.


Quote:
Originally Posted by lukedamrosch View Post
On an unrelated note, did you happen to try the ELM-C in M-S configuration and, if so, with what mic(s) for the S channel? I'm curious how flexible (or not) the ELM mics may be in that scenario, bearing in mind the considerable geometric mismatch between a long rectangular membrane and (e.g.) a small circular one for the figure 8.
No, I didn’t get to try it but the thought was on my mind a lot when I was considering a pair of ELM-As as my desert island mic pair. And here’s what I resolved if I’d ended up with a pair of ELM-As. Due to the length of the diaphragms, it would be silly to put one above the other for MS – there’ll be at least 8cm between diaphragms (centre to centre). Instead, I decided I would use Rolo’s approach of putting one behind the other. His recordings sound fine and, if you think about it, the worse case comb filtering scenario would occur with sounds arriving at ±45° off-axis in the horizontal plane, FWIW... I never got to try it, but I’ve been thinking of taking the same approach with my MKH800s to see how it goes...
Old 28th July 2020
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Thanks very much for these further thoughts and suggestions.

Your technique of monitoring via Nagra while adjusting the Milabs does indeed seem like a good method by which I could quickly and efficiently become more familiar with the nuances of "rectangular pickup" while on-site for a job. Usually I am more control-room-bound, as you described.

Good point as well about the similarity between the ELM's and ribbons in terms of directivity.

I'm very glad to hear your generally positive impression of the directivity (at least for the Milabs) in orchestral (or larger ensemble) recording scenarios. I have been in touch with Mattias from Milab/Pearl, who has been very helpful answering some questions and was also of the opinion, based on their users in the classical world, that the ELM mics should not be too narrow in the vertical plane for this kind of situation, albeit with some extra care in position potentially required.

If/when you happen to see this and have a moment, I'd be especially curious to hear your thoughts about the Milabs in omni mode? Obviously some of the well-known staples in the dual-output palette, like the MKH800/Twin, sound fantastic as omnis. What with the unorthodox pickup pattern, I'm very curious about how usable the Milab/Pearl mics are in omni -- especially the ELMs! -- compared to more familiar options. To be clear, I have no doubt their general frequency response and tonality are excellent, but the ELM-A for example even as low as 8kHz is already apparently about -15dB down at ±40-50° off-axis in the vertical plane. So, in practice, I wonder to what extent this could create some potential issues or unpredictable behavior compared to a more spherically symmetrical traditional omni.

Yes, your approach RE using the ELMs in M-S is exactly what I am intending to try when I'm able to properly demo a pair. Even if a SDC is used for the S mic, I suppose it might still give better-sounding results, by ensuring the differently dimensioned capsules are as close to coincident as possible with respect to the diaphragm centres.

With gratitude again for your always thoughtful and helpful advice/anecdotes,
Luke
Old 1st August 2020
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Quote:
Originally Posted by lukedamrosch View Post
Your technique of monitoring via Nagra while adjusting the Milabs does indeed seem like a good method...
I use that approach all the time now, even when placing close mics and spotters. It really does speed things up.


Quote:
Originally Posted by lukedamrosch View Post
I'm very glad to hear your generally positive impression of the directivity (at least for the Milabs) in orchestral (or larger ensemble) recording scenarios.
It’s just another parameter to use. Sometimes it’s not what you want, but it’s nice to have it when you need it. I cannot remember a time when it was a disadvantage.


Quote:
Originally Posted by lukedamrosch View Post
I have been in touch with Mattias from Milab/Pearl, who has been very helpful answering some questions and was also of the opinion, based on their users in the classical world, that the ELM mics should not be too narrow in the vertical plane for this kind of situation, albeit with some extra care in position potentially required.
I suspect they might be more useful than the DC196s in that respect. One thing I often wished with the DC196s was that the effect was a bit more pronounced, to be honest.


Quote:
Originally Posted by lukedamrosch View Post
If/when you happen to see this and have a moment, I'd be especially curious to hear your thoughts about the Milabs in omni mode?
I wish I could remember what I used them for in omni mode!

Most of the recordings I remember them for are ones where I came out from a difficult situation with an unexpectedly acceptable recording. Sometimes that was just due to the DC196’s small size and versatility, other times it was specifically due to the vertical off-axis behaviour.

Most of those situations were ORTF or Faulkner 2-Way Phased Array. The latter was used for a series of concerts in a room with a low ceiling and interesting acoustics (the Utzon Room at Sydney Opera House), where the mics were probably no more than 60cm below the ceiling itself. I would intentionally angle the mics to put the ceiling reflection into the vertical axis, which was already being rejected by the bidirectional response anyway.

I think the Mahler recording I linked in my earlier comment was omnis, and I was very happy with how that turned out under the circumstances (no mics on stage, etc.). I know for sure on that recording that the Milab’s vertical rejection was very effective for balancing the woodwinds against the strings, and I specifically used it that way...


Quote:
Originally Posted by lukedamrosch View Post
To be clear, I have no doubt their general frequency response and tonality are excellent, but the ELM-A for example even as low as 8kHz is already apparently about -15dB down at ±40-50° off-axis in the vertical plane. So, in practice, I wonder to what extent this could create some potential issues or unpredictable behavior compared to a more spherically symmetrical traditional omni.
I think it depends on how much value you place on information arriving from the vertical plane. Certainly it might be an issue spot-miking a double bass or similar (although turning the mic sideways would probably do a good job while also rejecting sounds to the sides a little bit). But for any distant miking my personal aesthetic sees it as an advantage.

I’m sure there are plenty who will disagree with me on this, but my ideal polar response would be toroidal. I’m really into creating or capturing a sense of spaciousness in my recordings, and in pursuit of that I’ve learnt that “lateral early reflections = good, vertical early reflections = bad”. So to me, the ideal polar response for distant miking an acoustic ensemble in a concert hall or similar would be the equivalent of taking the front of a bidirectional and rotating it through 360° to create a donut or toroid shape that captures lateral information but rejects vertical information. The ELM-A in omni mode comes to the closest to that ideal that I can think of.

Last edited by Simmosonic; 4th August 2020 at 01:18 AM..
Old 2nd August 2020
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I like the toroidal thought.
Old 3rd August 2020
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Originally Posted by emrr View Post
I like the toroidal thought.
Laying in bed thinking of ways to create it is my equivalent to counting sheep!

I’m pretty sure it could be done with an omni combined with upward and downfacing hypercardioids mixed in with inverted polarity. Also pretty sure it could be derived from an ambisonic mic or something like Core Sounds’ Octomic. In all cases, however, that approach needs a lot of tracks to do – especially in stereo.

The more appealing thought to me is small absorptive baffles around the mic array, so each channel requires a single track. So I start thinking about how large those baffles need to be and how to place them around the mic and by that time zzzzzz....

I have seen one or two commercial offerings but they’re usually for dialogue in conference rooms and similar specific limited bandwidth applications.
Old 3rd August 2020
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@ Simmosonic instead of experimenting with two hypercardiods nulled, how about a single Figure-8? 😀
Old 3rd August 2020
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Quote:
Originally Posted by Klimermonk View Post
@ Simmosonic instead of experimenting with two hypercardiods nulled, how about a single Figure-8? 😀
The hypers would null against the omni, I think. The 8 would either cancel itself and do nothing, or add to one or the other side of the omni.
Old 4th August 2020
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Quote:
Originally Posted by Simmosonic View Post
I’m pretty sure it could be done with an omni combined with upward and downfacing hypercardioids mixed in with inverted polarity.
I have an MKH 800 Twin and an MKH 20 to try this with ASAP.
Old 4th August 2020
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Quote:
Originally Posted by Klimermonk View Post
@ Simmosonic instead of experimenting with two hypercardiods nulled, how about a single Figure-8? ������
Ha! That was one my first ideas, but only for a second until I realised that’s how we make a cardioid. If in correct polarity, the rear lobe of the bidirectional will cancel out with the omni while the front lobe will reinforce. That’s a cardioid. And if we invert the polarity of the bidirectional we just end up with a cardioid facing the other direction.

If you could separate the signal from the front and rear lobes of the bidirectional, that would do it. But that’s not how a bidirectional works or is created. Hence we’re back to the two cardioids or two supercardioids, one facing up from above the omni and one facing down from below the omni, both inverted polarity and cancelling from the omni.

I think that would be one way to do it without resorting to baffles, but it depends on just how much (in terms of lateral reflections) those up and down mics are capturing and therefore cancelling. They might not be directional enough.

I’m also thinking a lot about boundary mics with their hemispherical response...

- Greg Simmons
Old 4th August 2020
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Quote:
Originally Posted by emrr View Post
I have an MKH 800 Twin and an MKH 20 to try this with ASAP.
Let me know how it goes. Presumably you’re going to derive from the MKH800 an upward facing and downward facing hypercardioid or similar?
Old 4th August 2020
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Yes, of course you're right. I'd forgotten we were dealing with a mono signal.

The MKH80 (or Pearl dual output) idea is good though - invert the front lobe only I suppose...

This could perhaps be done more easily with a Soundfield!
Old 4th August 2020
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Quote:
Originally Posted by Simmosonic View Post
I use that approach all the time now, even when placing close mics and spotters. It really does speed things up.
I'll be trying it on my next recording session at the end of the month. With luck, I may even have a demo pair of ELM-A on-hand at the time. Thanks for the reminder RE this technique.


Quote:
Originally Posted by Simmosonic View Post
It’s just another parameter to use. Sometimes it’s not what you want, but it’s nice to have it when you need it. I cannot remember a time when it was a disadvantage.
Glad to hear this, thank you again for all your valuable thoughts on these practical concerns.


Quote:
Originally Posted by Simmosonic View Post
I think the Mahler recording I linked in my earlier comment was omnis, and I was very happy with how that turned out under the circumstances (no mics on stage, etc.). I know for sure on that recording that the Milab’s vertical rejection was very effective for balancing the woodwinds against the strings, and I specifically used it that way...
I was wondering if that might have been the case. And, yes, with the ever-increasing primacy of how things like this will look on video, the ability to have more balance control "from above" with this kind of capsule is very appealing.


Quote:
Originally Posted by Simmosonic View Post
I think it depends on how much value you place on information arriving from the vertical plane.
Well said I suppose I'll have to form my own conclusions after properly demoing these whenever that can be arranged/managed.


Quote:
Originally Posted by Simmosonic View Post
I’m sure there are plenty who will disagree with me on this, but my ideal polar response would be toroidal
I agree that this is a very interesting concept.
Old 4th August 2020
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the gefell line array mic - in some ways - comes close to a toroidal pattern:

https://www.microtechgefell.de/datei...ofon_OaQcr.pdf

the graphs do not reflect the impression well which i was getting: imo the pattern is more like a 'toroid cut in half' - too bad the mic is extremely expensive (for obvious reason)...

on those rare occasion when i felt it was absolutely needed (not the typical application for hi-level talking heads but to capture a choir standing below an organ, trying to avoid the organ getting in the choir mics), i can assure you that it allowed me to achieve results i cannot imagine i could have gotten by using any other mic, mic array and/or mic system with steering capability/dematrixing option!
Old 4th August 2020
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Quote:
Originally Posted by Simmosonic View Post
Let me know how it goes. Presumably you’re going to derive from the MKH800 an upward facing and downward facing hypercardioid or similar?
Exactly
Old 5th August 2020
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Originally Posted by deedeeyeah View Post
the graphs do not reflect the impression well which i was getting: imo the pattern is more like a 'toroid cut in half' - too bad the mic is extremely expensive (for obvious reason)...
Wow, that’s an interesting microphone indeed!

I have seen it before, as a picture, but never bothered to learn anything about it. Your post and opinion says a lot.

Does it sound okay for music?

But, as you said... the price. :-(
Old 5th August 2020
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Quote:
Originally Posted by Simmosonic View Post
Wow, that’s an interesting microphone indeed!

I have seen it before, as a picture, but never bothered to learn anything about it. Your post and opinion says a lot.

Does it sound okay for music?

But, as you said... the price. :-(
i'm not getting into situations often enough which would justify the expenses (and when i did 'need' these mics, i was lucky enough i could rent a pair; however, corona might change that...) but in those situations i used them (actually the former model 970), they fared very well.

maybe worth noting though that i never used these mics under 'normal' conditions and hence did not attempt to compare them with any other mics (which i ruled out in the first place); in my applications, signals needed a fair amount of tweaking but i'm convinced this was due to the very challenging conditions and not down to an intrinsic 'issue' with these mics!

upon listening to the results, no one knew that radically different mics than the typical schoeps, neuheiser, b&k etc. were used; some folks who were involved in the production and know a bit about recording were amazed by the amount of separation/definition i could get without the organ overpowering the choir - pretty impressive! :-)
Old 6th August 2020
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Quote:
Originally Posted by deedeeyeah View Post
upon listening to the results, no one knew that radically different mics than the typical schoeps, neuheiser, b&k etc. were used; some folks who were involved in the production and know a bit about recording were amazed by the amount of separation/definition i could get without the organ overpowering the choir - pretty impressive! :-)
The choir under the organ is a great test and example! I can relate to that problem and can picture the Gefell’s vertical polar response saving the day. I’m glad you mentioned that mic, it’s very handy to know about...
Old 6th August 2020
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Also the choir above the timpani or above the brass. I have used them (the hall had them) to minimize the those.
Old 8th August 2020
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Quote:
Originally Posted by Simmosonic View Post
Let me know how it goes. Presumably you’re going to derive from the MKH800 an upward facing and downward facing hypercardioid or similar?
I just tried it with an MKH 800 Twin and a 4060, it does work, crudely. I put a metronome on the end of 18" of string and ran a circle slowly around the mic pair to maintain distance and level as best as possible.

Best set supercardioid in my test. When you are at 90/270º relative to the supers, you get maximum output from the mono array of 3. It may not be a toroid, but it's at least a greatly flattened sphere, less output up and down, more side to side. It's not purely with respect to frequency (beamy nature of the MKH 800 at the top), but that has value in practice as well.
Old 8th August 2020
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Quote:
Originally Posted by emrr View Post
Best set supercardioid in my test. When you are at 90/270º relative to the supers, you get maximum output from the mono array of 3. It may not be a toroid, but it's at least a greatly flattened sphere, less output up and down, more side to side. It's not purely with respect to frequency (beamy nature of the MKH 800 at the top), but that has value in practice as well.
Oh, that’s interesting! Thank you testing the idea.

A flattened sphere might be all it needs to be to reduce the level of the vertical reflections sufficiently.

I’m assuming it would be a lot easier to do with ambisonic mic, or even the Octomic. But for doing it in stereo with the Octomic would require 16 tracks.
Old 10th August 2020
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Originally Posted by Simmosonic View Post
A flattened sphere might be all it needs to be to reduce the level of the vertical reflections sufficiently.
I've been going over the toroidal concept in my mind for the past few days. Interesting to think about this.

In a situation where the main mic system is perhaps 3-4 meters above the floor of the performance space, this would imply (for a reasonably large room/hall) that the floor is considerably closer than any other boundary, assuming a decently high ceiling.

Therefore it seems intuitive that removing a certain amount of floor reflections could improve clarity, whether by mitigating "muddying" localization cues or tonal colorations due to these reflections.

Obviously this would be just as true but in reverse for a situation, like what you described above, where the mics are much closer to the ceiling.

Besides this potential benefit of a "toroidal" pickup, were there other implications I am neglecting to notice from your axiom "lateral early reflections = good, vertical early reflections = bad" ?
Old 10th August 2020
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i do not agree that early reflection are 'mudding' the soundfield, on the contrary: when trying to achieve best possible localisation within the soundfield, besides using coincident mics, getting enough early reflections is mandatory.

you can easily try this by either flying mics very high or using blm's/pzm's: localisation from both systems is poor compared to results from a pair of mics positioned at 'normal' height.

i don't agree on the claim that there 'good' or 'bad' early reflections either: adding random early reflections via artificial efx can beef up the general soundfield but one needs typical early reflections from the room to get a 'natural' portray: reflections are coming from different directions and only together characterize a specific room.

(i do not always want to position an instrument positioned on the far side of an orchestra to appear in the actual position in the mix though: i then try avoiding capturing too many early reflections as it will help to blur the image a bit).
Old 11th August 2020
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Quote:
Originally Posted by lukedamrosch View Post
Therefore it seems intuitive that removing a certain amount of floor reflections could improve clarity, whether by mitigating "muddying" localization cues or tonal colorations due to these reflections.
That does seem intuitive and I like to think it’s true. However, I’ve also made recordings that have intentionally cancelled out the floor reflection and sometimes if I close my eyes and listen to those recordings it feels like the ensemble is floating in the air, or that I’m floating in the air somewhere above it. I think those recordings really need that floor reflection ‘anchor’.

Of all the vertical reflections, the floor is the most tricky to mess with because it is with us all the time – except while parachuting, etc.! When miking an instrument relatively close (30cm to 1m or so?) I will go to great lengths to kill any floor reflections that might be causing comb filtering, but when distant miking an ensemble I think a bit of it is helpful...

Quote:
Originally Posted by lukedamrosch View Post
Besides this potential benefit of a "toroidal" pickup, were there other implications I am neglecting to notice from your axiom "lateral early reflections = good, vertical early reflections = bad" ?
Were there other implications you neglected to notice? I’ve no idea, but here’s some background...

This little maxim of mine is derived from work by acoustician Heinrich Kuttruff, who looked into the factors behind why some concert halls were considered to sound more ‘spacious’ than others, despite careful up-to-date acoustic design and so on.

One of Kuttruff’s criteria for creating a subjective sense of spaciousness in a concert hall states that the early reflections must arrive at the listener from lateral directions and be within certain time, amplitude and correlation windows relative to the direct sound.

So, if I want to capture and embed that sense of spaciousness in a recording then I would choose microphones and placements that allow me to focus on the most apt lateral reflections. Hence, the notion of a polar response that rejects vertical reflections is a good start.

There’s a lot more to Kuttruff’s work than that, of course, but I think you get the idea. I lost count of how many times I read through his book ‘Room Acoustics’, which contains all of this information. But that was many years ago: in the early to mid ‘80s when I was very much into trying to add ‘spaciousness’ to my multitrack studio mixes. To that end, I spent weeks coding a room simulator algorithm (BASIC on an Apple IIC, I called it ‘Sound Stage’, LOL!), then I hired a multitrack studio for a weekend, along with a whole bunch of digital delays (mostly SPX90s). At the time I had intended this to be the beginnings of a commercial product, perhaps something like Quantec’s Room Simulator, which I loved the effect of.

In the studio, I started creating the spaces using the figures from the program: delay time, amplitude, spectrum, etc., and feeding an electronically generated signal into them. It quickly became clear that vertical reflections really were not helpful when rendered through a stereo pair of speakers; it turned them into lateral reflections that conflicted with the intended lateral reflections. They created the sense of additional side walls at different distances to the intended side walls, and therefore ‘blurred’ the spatial image I was trying to create and confused the sense of spaciousness – which is also why I don’t want them in my recordings.

It was an interesting experiment. I never took it to the level of a commercial product after that; apart from having no money to do it (LOL!) it seemed I had figured out what I wanted to know to translate Kuttruff’s criteria for spaciousness in concert hall design into an approach I could build into my recordings and mixes. It just became part of my recording ‘toolbox’ I suppose.

[I should also add that the tip-off to Kuttruff’s book came from an article in Recording Engineer/Producer magazine, which discussed Kuttruff’s criteria for spaciousness and suggested ways of using them in our mixing. It was an inspiring and motivating read; I cannot remember who wrote it...]

As I said when I first brought up the toroidal polar response idea, “I’m sure there are plenty who will disagree with me on this...” It’s no different to discussing our preferences for omni vs cardioid, coffee vs tea, or whatever!
Old 11th August 2020
  #28
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Quote:
Originally Posted by deedeeyeah View Post
i don't agree on the claim that there 'good' or 'bad' early reflections either: adding random early reflections via artificial efx can beef up the general soundfield but one needs typical early reflections from the room to get a 'natural' portray: reflections are coming from different directions and only together characterize a specific room.
My take on this is best explained in my reply to lukedamrosch [see post 27]

Essentially, if you are working in stereo, the person listening to a playback of the recording has lost the ability to determine which direction the reflections originated from. When reproduced through a stereo pair of speakers, all the reflections captured by the microphone will arrive from the front or sides. So all those other early reflections (including vertical and back wall) are now all arriving from the front and sides of the listener (around to ±30° or so), creating the effect of multiple front and side walls at different distances. It is the effect of a room within a room, or more...

The question for me has always been “how many reflections do you need to create the impression of the size of a room?” It is very few. If you add too many it just clutters the image. If I have reflections initially coming from the ceiling and the rear wall but now being reproduced through stereo speakers as frontal and lateral directions, they are not helpful.

The reverberation is helpful and it’s good to capture that as well as we can, but I believe we need to be very careful with which early reflections we capture in the process. Thankfully, the early reflections are directional, while reverberation is not.
Old 11th August 2020
  #29
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Quote:
Originally Posted by Simmosonic View Post
My take on this is best explained in my reply to lukedamrosch [see post 27]

Essentially, if you are working in stereo, the person listening to a playback of the recording has lost the ability to determine which direction the reflections originated from.
no: a recording made with typical omnis, flying high and far from any boundary with added artificial early reflection yields poor localisation - a recording made with the identical set if omnis flying lower, at a typical height of ca. 3,5m yields better localisation within the stero soundfield.


Quote:
Originally Posted by Simmosonic View Post
When reproduced through a stereo pair of speakers, all the reflections captured by the microphone will arrive from the front or sides. So all those other early reflections (including vertical and back wall) are now all arriving from the front and sides of the listener (around to ±30° or so), creating the effect of multiple front and side walls at different distances. It is the effect of a room within a room, or more...
that's neither true on the recording side nor on the playback side...

Quote:
Originally Posted by Simmosonic View Post
The question for me has always been “how many reflections do you need to create the impression of the size of a room?” It is very few. If you add too many it just clutters the image. If I have reflections initially coming from the ceiling and the rear wall but now being reproduced through stereo speakers as frontal and lateral directions, they are not helpful.

The reverberation is helpful and it’s good to capture that as well as we can, but I believe we need to be very careful with which early reflections we capture in the process. Thankfully, the early reflections are directional, while reverberation is not.
i guess we're talking about different things: i didn't say we need early reflections to determine the room size - what i said is that they support the localication withing the stereo or surround field, a fact that gets even used to our advantage in the speaker and studio design:

i don't agree on the idea that during reproduction er's are all stemming from just two dimensions/a narrow angle: lower frequencies simply 'wrap around' speakers and typical studio monitors and hifi speakers use soft dome tweeters which are not much directional, certainly not when compared to horn-loaded soeakers as used in live sr...

the simplified idea goes out of the window by looking at typical control rooms designs and speaker setups used in most everyone's living room (and speaker behaviour, see above) - even more so when talking about surround and immersive firmats: one gets early reflections coming from all different sides...

same for recording in small rooms: unless we're talking about amplified instruments (and directional combos/stacks), early reflections get picked up coming from all sides, not just within a relatively small angle - certainly when using omnis: there is front, rear, bottom ceiling and side wall bouncing of er's, all arriving at different times and from all different angles...

in a typical large hall recording scenario, there are not that many early reflections and mainly (if not exclusively) stemming from the floor so imo there almost cannot be 'too many' er's unless we're talking about using tons of omnis for spots; then too many (or better: a too high amount of) er's can indeed clutter the image while 'not enough' to my ears leads to an anemic soundfield which plagues quite a few productions...
Old 11th August 2020
  #30
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Quote:
Originally Posted by Simmosonic View Post
Were there other implications you neglected to notice? I’ve no idea, but here’s some background...
Haha! Fair enough. I'm fairly certain there were/are, but nevertheless thank you very much for your characteristically thoughtful and thorough response.
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